Download Sensory Part 3

Special Senses
Organs of Equilibrium
 Equilibrium receptors of the inner ear are called the
vestibular apparatus
 Vestibular apparatus has two functional parts
 Static equilibrium
 Dynamic equilibrium
Organs of Equilibrium
Figure 8.14a–b
Static Equilibrium
 Maculae—receptors in the vestibule
 Report on the position of the head
 Send information via the vestibular nerve
 Anatomy of the maculae
 Hair cells are embedded in the otolithic membrane
 Otoliths (tiny stones) float in a gel around the hair cells
 Movements cause otoliths to bend the hair cells
Structure and Function of Maculae
Figure 8.13a
Structure and Function of Maculae
Figure 8.13b
Dynamic Equilibrium
 Crista ampullaris—receptors in the semicircular canals
 Tuft of hair cells
 Cupula (gelatinous cap) covers the hair cells
Dynamic Equilibrium
Figure 8.14c
Dynamic Equilibrium
 Action of angular head movements
 The cupula stimulates the hair cells
 An impulse is sent via the vestibular nerve to the cerebellum
Organs of Hearing
 Organ of Corti
 Located within the cochlea
 Receptors = hair cells on the basilar membrane
 Gel-like tectorial membrane is capable of bending hair cells
 Cochlear nerve attached to hair cells transmits nerve impulses
to auditory cortex on temporal lobe
Organs of Hearing
Figure 8.15a
Organs of Hearing
Figure 8.15b
Mechanism of Hearing
 Vibrations from sound waves move tectorial membrane
 Hair cells are bent by the membrane
 An action potential starts in the cochlear nerve
 Continued stimulation can lead to adaptation
Mechanism of Hearing
Figure 8.16a
Mechanism of Hearing
Figure 8.16b–c
Olfaction—The Sense of Smell
 Olfactory receptors are in the roof of the nasal cavity
 Neurons with long cilia
 Chemicals must be dissolved in mucus for detection
 Impulses are transmitted via the olfactory nerve
 Interpretation of smells is made in the cortex
Olfactory Epithelium
Figure 8.17
The Sense of Taste
 Taste buds house the receptor organs
 Location of taste buds
 Most are on the tongue
 Soft palate
 Cheeks
Taste Buds
Figure 8.18
The Tongue and Taste
 The tongue is covered with projections called papillae
 Filiform papillae—sharp with no taste buds
 Fungifiorm papillae—rounded with taste buds
 Circumvallate papillae—large papillae with taste buds
 Taste buds are found on the sides of papillae
Structure of Taste Buds
 Gustatory cells are the receptors
 Have gustatory hairs (long microvilli)
 Hairs are stimulated by chemicals dissolved in saliva
Structure of Taste Buds
 Impulses are carried to the gustatory complex by several
cranial nerves because taste buds are found in different areas
 Facial nerve
 Glossopharyngeal nerve
 Vagus nerve
Taste Sensations
 Sweet receptors
 Saccharine
 Some amino acids
 Sour receptors
 Acids
 Bitter receptors
 Alkaloids
 Salty receptors
 Metal ions
(sugars)
Developmental Aspects of the Special
Senses
 Formed early in embryonic development
 Eyes are outgrowths of the brain
 All special senses are functional at birth
Chemical Senses: Taste and Smell
 Both senses use chemoreceptors
 Stimulated by chemicals in solution
 Taste has four types of receptors
 Smell can differentiate a large range of chemicals
 Both senses complement each other and respond to many of
the same stimuli
Developmental Aspects of the
Special Senses
 Eye problems
 Strabismus—“crossed eyes” results from unequal pulls by the
external eye muscles in babies
 Ophthalmia neonatorum—conjunctivitis resulting from mother
having gonorrhea. Baby’s eyelids are swollen and pus is
produced
Developmental Aspects of the
Special Senses
 Eye problems
 Presbyopia—“old vision” results from decreasing lens elasticity
that accompanies aging
Developmental Aspects of the
Special Senses
 Ear problems
 Presbycusis—type of sensorineural deafness
 Otosclerosis—ear ossicles fuse